Insect and other pests can cause injury and even death by their bites or stings. Additionally, many pests transmit bacteria and other pathogens that cause diseases. For example, mosquitoes transmit pathogens that cause malaria, yellow fever, encephalitis, and other diseases. The bubonic plague, or black death, is caused by bacteria that infect rats and other rodents. Compositions for controlling microscopic pest infestations have been provided in the form of antibiotic, antiviral, and antifungal compositions. Methods for controlling infestations by pests, such as nematodes and insects, have typically been in the form of chemical compositions that are applied to surfaces on which pests reside, or administered to infested animals in the form of pellets, powders, tablets, pastes, or capsules.
Control of insect pests on agronomically important crops is an important field, for instance insect pests which damage plants belonging to the Solanaceae family, especially potato (Solanum tuberosum), but also tomato (Solanum lycopersicum), eggplant (Solanum melongena), capsicums (Solanum capsicum), and nightshade (for example, Solanum aculeastrum, S. bulbocastanum, S. cardiophyllum, S. douglasii, S. dulcamara, S. lanceolatum, S. robustum, and S. triquetrum), particularly the control of coleopteran pests.
Substantial progress has been made in the last few decades towards developing more efficient methods and compositions for controlling insect infestations in plants. Chemical pesticides have been very effective in eradicating pest infestations.
Biological control using extract from neem seed has been shown to work against coleopteran pests of vegetables. Commercially available neem-based insecticides have azadirachtin as the primary active ingredient. These insecticides are applicable to a broad spectrum of insects. They act as insect growth regulator; azadirachtin prevents insects from molting by inhibiting production of an insect hormone, ecdysone.
Biological control using protein Cry3A from Bacillus thuringiensis varieties tenebrionis and san diego, and derived insecticidal proteins are alternatives to chemical control. The Bt toxin protein is effective in controlling Colorado potato beetle larvae either as formulations sprayed onto the foliage or expressed in the leaves of potatoes.
An alternative biological agent is dsRNA. Over the last few years, down-regulation of genes (also referred to as “gene silencing”) in multicellular organisms by means of RNA interference or “RNAi” has become a well-established technique.
RNA interference or “RNAi” is a process of sequence-specific down-regulation of gene expression (also referred to as “gene silencing” or “RNA-mediated gene silencing”) initiated by double-stranded RNA (dsRNA) that is complementary in sequence to a region of the target gene to be down-regulated (Fire, A. Trends Genet. Vol. 15, 358-363, 1999; Sharp, P. A. Genes Dev. Vol. 15, 485-490, 2001).
Over the last few years, down-regulation of target genes in multicellular organisms by means of RNA interference (RNAi) has become a well established technique. Reference may be made to International Applications WO 99/32619 (Carnegie Institution) and WO 00/01846 (by Applicant).
DsRNA gene silencing finds application in many different areas, such as for example dsRNA mediated gene silencing in clinical applications (WO2004/001013) and in plants. In plants, dsRNA constructs useful for gene silencing have also been designed to be cleaved and to be processed into short interfering RNAs (siRNAs).
Although the technique of RNAi has been generally known in the art in plants, C. elegans and mammalian cells for some years, to date little is known about the use of RNAi to down-regulate gene expression in insects. Since the filing and publication of the WO 00/01846 and WO 99/32619 applications, only few other applications have been published that relate to the use of RNAi to protect plants against insects. These include the International Applications WO 01/37654 (DNA Plant Technologies), WO 2005/019408 (Bar Ilan University), WO 2005/049841 (CSIRO, Bayer Cropscience), WO 05/047300 (University of Utah Research foundation), and the US application 2003/00150017 (Mesa et al.). The present invention provides target genes and constructs useful in the RNAi-mediated insect pest control. Accordingly, the present invention provides methods and compositions for controlling pest infestation by repressing, delaying, or otherwise reducing gene expression within a particular pest.